1 files changed, 235 insertions, 0 deletions
diff --git a/dom/media/webaudio/DelayBuffer.cpp b/dom/media/webaudio/DelayBuffer.cpp
new file mode 100644
index 0000000000..cab2920080
--- /dev/null
+++ b/dom/media/webaudio/DelayBuffer.cpp
@@ -0,0 +1,235 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "DelayBuffer.h"
+
+#include "mozilla/PodOperations.h"
+#include "AudioChannelFormat.h"
+#include "AudioNodeEngine.h"
+
+namespace mozilla {
+
+size_t DelayBuffer::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
+  size_t amount = 0;
+  amount += mChunks.ShallowSizeOfExcludingThis(aMallocSizeOf);
+  for (size_t i = 0; i < mChunks.Length(); i++) {
+    amount += mChunks[i].SizeOfExcludingThis(aMallocSizeOf, false);
+  }
+
+  amount += mUpmixChannels.ShallowSizeOfExcludingThis(aMallocSizeOf);
+  return amount;
+}
+
+void DelayBuffer::Write(const AudioBlock& aInputChunk) {
+  // We must have a reference to the buffer if there are channels
+  MOZ_ASSERT(aInputChunk.IsNull() == !aInputChunk.ChannelCount());
+#ifdef DEBUG
+  MOZ_ASSERT(!mHaveWrittenBlock);
+  mHaveWrittenBlock = true;
+#endif
+
+  if (!EnsureBuffer()) {
+    return;
+  }
+
+  if (mCurrentChunk == mLastReadChunk) {
+    mLastReadChunk = -1;  // invalidate cache
+  }
+  mChunks[mCurrentChunk] = aInputChunk.AsAudioChunk();
+}
+
+void DelayBuffer::Read(const float aPerFrameDelays[WEBAUDIO_BLOCK_SIZE],
+                       AudioBlock* aOutputChunk,
+                       ChannelInterpretation aChannelInterpretation) {
+  int chunkCount = mChunks.Length();
+  if (!chunkCount) {
+    aOutputChunk->SetNull(WEBAUDIO_BLOCK_SIZE);
+    return;
+  }
+
+  // Find the maximum number of contributing channels to determine the output
+  // channel count that retains all signal information.  Buffered blocks will
+  // be upmixed if necessary.
+  //
+  // First find the range of "delay" offsets backwards from the current
+  // position.  Note that these may be negative for frames that are after the
+  // current position (including i).
+  float minDelay = aPerFrameDelays[0];
+  float maxDelay = minDelay;
+  for (unsigned i = 1; i < WEBAUDIO_BLOCK_SIZE; ++i) {
+    minDelay = std::min(minDelay, aPerFrameDelays[i] - i);
+    maxDelay = std::max(maxDelay, aPerFrameDelays[i] - i);
+  }
+
+  // Now find the chunks touched by this range and check their channel counts.
+  int oldestChunk = ChunkForDelay(std::ceil(maxDelay));
+  int youngestChunk = ChunkForDelay(std::floor(minDelay));
+
+  uint32_t channelCount = 0;
+  for (int i = oldestChunk; true; i = (i + 1) % chunkCount) {
+    channelCount =
+        GetAudioChannelsSuperset(channelCount, mChunks[i].ChannelCount());
+    if (i == youngestChunk) {
+      break;
+    }
+  }
+
+  if (channelCount) {
+    aOutputChunk->AllocateChannels(channelCount);
+    ReadChannels(aPerFrameDelays, aOutputChunk, 0, channelCount,
+                 aChannelInterpretation);
+  } else {
+    aOutputChunk->SetNull(WEBAUDIO_BLOCK_SIZE);
+  }
+}
+
+void DelayBuffer::ReadChannel(const float aPerFrameDelays[WEBAUDIO_BLOCK_SIZE],
+                              AudioBlock* aOutputChunk, uint32_t aChannel,
+                              ChannelInterpretation aChannelInterpretation) {
+  if (!mChunks.Length()) {
+    float* outputChannel = aOutputChunk->ChannelFloatsForWrite(aChannel);
+    PodZero(outputChannel, WEBAUDIO_BLOCK_SIZE);
+    return;
+  }
+
+  ReadChannels(aPerFrameDelays, aOutputChunk, aChannel, 1,
+               aChannelInterpretation);
+}
+
+void DelayBuffer::ReadChannels(const float aPerFrameDelays[WEBAUDIO_BLOCK_SIZE],
+                               AudioBlock* aOutputChunk, uint32_t aFirstChannel,
+                               uint32_t aNumChannelsToRead,
+                               ChannelInterpretation aChannelInterpretation) {
+  uint32_t totalChannelCount = aOutputChunk->ChannelCount();
+  uint32_t readChannelsEnd = aFirstChannel + aNumChannelsToRead;
+  MOZ_ASSERT(readChannelsEnd <= totalChannelCount);
+
+  if (mUpmixChannels.Length() != totalChannelCount) {
+    mLastReadChunk = -1;  // invalidate cache
+  }
+
+  for (uint32_t channel = aFirstChannel; channel < readChannelsEnd; ++channel) {
+    PodZero(aOutputChunk->ChannelFloatsForWrite(channel), WEBAUDIO_BLOCK_SIZE);
+  }
+
+  for (unsigned i = 0; i < WEBAUDIO_BLOCK_SIZE; ++i) {
+    float currentDelay = aPerFrameDelays[i];
+    MOZ_ASSERT(currentDelay >= 0.0f);
+    MOZ_ASSERT(currentDelay <= (mChunks.Length() - 1) * WEBAUDIO_BLOCK_SIZE);
+
+    // Interpolate two input frames in case the read position does not match
+    // an integer index.
+    // Use the larger delay, for the older frame, first, as this is more
+    // likely to use the cached upmixed channel arrays.
+    int floorDelay = int(currentDelay);
+    float interpolationFactor = currentDelay - floorDelay;
+    int positions[2];
+    positions[1] = PositionForDelay(floorDelay) + i;
+    positions[0] = positions[1] - 1;
+
+    for (unsigned tick = 0; tick < ArrayLength(positions); ++tick) {
+      int readChunk = ChunkForPosition(positions[tick]);
+      // The zero check on interpolationFactor is important because, when
+      // currentDelay is integer, positions[0] may be outside the range
+      // considered for determining totalChannelCount.
+      // mVolume is not set on default initialized chunks so also handle null
+      // chunks specially.
+      if (interpolationFactor != 0.0f && !mChunks[readChunk].IsNull()) {
+        int readOffset = OffsetForPosition(positions[tick]);
+        UpdateUpmixChannels(readChunk, totalChannelCount,
+                            aChannelInterpretation);
+        float multiplier = interpolationFactor * mChunks[readChunk].mVolume;
+        for (uint32_t channel = aFirstChannel; channel < readChannelsEnd;
+             ++channel) {
+          aOutputChunk->ChannelFloatsForWrite(channel)[i] +=
+              multiplier * mUpmixChannels[channel][readOffset];
+        }
+      }
+
+      interpolationFactor = 1.0f - interpolationFactor;
+    }
+  }
+}
+
+void DelayBuffer::Read(float aDelayTicks, AudioBlock* aOutputChunk,
+                       ChannelInterpretation aChannelInterpretation) {
+  float computedDelay[WEBAUDIO_BLOCK_SIZE];
+
+  for (unsigned i = 0; i < WEBAUDIO_BLOCK_SIZE; ++i) {
+    computedDelay[i] = aDelayTicks;
+  }
+
+  Read(computedDelay, aOutputChunk, aChannelInterpretation);
+}
+
+bool DelayBuffer::EnsureBuffer() {
+  if (mChunks.Length() == 0) {
+    // The length of the buffer is at least one block greater than the maximum
+    // delay so that writing an input block does not overwrite the block that
+    // would subsequently be read at maximum delay.  Also round up to the next
+    // block size, so that no block of writes will need to wrap.
+    const int chunkCount = (mMaxDelayTicks + 2 * WEBAUDIO_BLOCK_SIZE - 1) >>
+                           WEBAUDIO_BLOCK_SIZE_BITS;
+    if (!mChunks.SetLength(chunkCount, fallible)) {
+      return false;
+    }
+
+    mLastReadChunk = -1;
+  }
+  return true;
+}
+
+int DelayBuffer::PositionForDelay(int aDelay) {
+  // Adding mChunks.Length() keeps integers positive for defined and
+  // appropriate bitshift, remainder, and bitwise operations.
+  return ((mCurrentChunk + mChunks.Length()) * WEBAUDIO_BLOCK_SIZE) - aDelay;
+}
+
+int DelayBuffer::ChunkForPosition(int aPosition) {
+  MOZ_ASSERT(aPosition >= 0);
+  return (aPosition >> WEBAUDIO_BLOCK_SIZE_BITS) % mChunks.Length();
+}
+
+int DelayBuffer::OffsetForPosition(int aPosition) {
+  MOZ_ASSERT(aPosition >= 0);
+  return aPosition & (WEBAUDIO_BLOCK_SIZE - 1);
+}
+
+int DelayBuffer::ChunkForDelay(int aDelay) {
+  return ChunkForPosition(PositionForDelay(aDelay));
+}
+
+void DelayBuffer::UpdateUpmixChannels(
+    int aNewReadChunk, uint32_t aChannelCount,
+    ChannelInterpretation aChannelInterpretation) {
+  if (aNewReadChunk == mLastReadChunk) {
+    MOZ_ASSERT(mUpmixChannels.Length() == aChannelCount);
+    return;
+  }
+
+  NS_WARNING_ASSERTION(mHaveWrittenBlock || aNewReadChunk != mCurrentChunk,
+                       "Smoothing is making feedback delay too small.");
+
+  mLastReadChunk = aNewReadChunk;
+  mUpmixChannels = mChunks[aNewReadChunk].ChannelData<float>().Clone();
+  MOZ_ASSERT(mUpmixChannels.Length() <= aChannelCount);
+  if (mUpmixChannels.Length() < aChannelCount) {
+    if (aChannelInterpretation == ChannelInterpretation::Speakers) {
+      AudioChannelsUpMix(&mUpmixChannels, aChannelCount,
+                         SilentChannel::ZeroChannel<float>());
+      MOZ_ASSERT(mUpmixChannels.Length() == aChannelCount,
+                 "We called GetAudioChannelsSuperset to avoid this");
+    } else {
+      // Fill up the remaining channels with zeros
+      for (uint32_t channel = mUpmixChannels.Length(); channel < aChannelCount;
+           ++channel) {
+        mUpmixChannels.AppendElement(SilentChannel::ZeroChannel<float>());
+      }
+    }
+  }
+}
+
+}  // namespace mozilla